The Gila Monster and the Origins of GLP-1 Medications

The medicines now in the news for weight management have an unlikely origin story: a lizard in the American Southwest. The path from a reptile’s venom to the modern GLP-1 medications took about three decades, and it is a good example of how basic science turns into medicine. This guide walks through the main steps. It is general education, not medical advice.

A hormone that does not last

GLP-1, short for glucagon-like peptide-1, is a hormone your gut releases after you eat. It helps your pancreas release insulin when blood sugar is high, slows the stomach’s emptying and signals fullness to the brain. Scientists described it in the 1980s and quickly saw its promise for type 2 diabetes. There was one big problem: the body’s own GLP-1 is broken down within minutes. Giving it as a medicine would not work.

The lizard clue

In the early 1990s, endocrinologist John Eng was studying hormones in the venom of the Gila monster, a slow-moving desert lizard, at a Veterans Affairs medical center in New York. In 1992 he and colleagues isolated a peptide called exendin-4. It shared about half of its building blocks with human GLP-1, and it acted on the same receptors. The important difference was that it lasted far longer in the bloodstream.

From lizard peptide to first medicine

• 2005: the first GLP-1 medicine. A synthetic version of exendin-4, called exenatide, was approved by the U.S. Food and Drug Administration for type 2 diabetes. It was taken twice a day.
• Around 2010: a longer-lasting design. Liraglutide was built from human GLP-1 with a small chemical change that helps it stay in the body longer, allowing once-daily use. People using it for diabetes also tended to lose some weight.
• 2014: a higher dose for weight. A higher-dose form of liraglutide was approved specifically for chronic weight management, the first GLP-1 medicine to be marketed for that purpose.
• 2017: weekly dosing. Semaglutide, modified to last about a week, was approved for type 2 diabetes.
• 2021: semaglutide for weight. A higher-dose form was approved for chronic weight management in adults.
• Beyond GLP-1 alone. Tirzepatide, which acts on the receptors for both GLP-1 and a related hormone called GIP, followed.

Why the design matters

• Each step solved a practical problem. Scientists made the molecule last longer, which meant fewer doses and steadier effects.
• The weight effect was noticed by watching people. In diabetes trials, many participants lost weight, which led researchers to test the medicines for that goal.
• The lizard did not do it alone. The natural compound was a starting point. The medicines in use today are engineered molecules.

What this history does and does not tell us

• It shows decades of testing. The medicines were studied in diabetes for many years before weight-management approvals, so there is a long record of safety data in that group.
• It does not mean they suit everyone. Side effects, cost and individual health all matter. Our guide to side effects in the big trials covers what participants reported.
• It does not replace habits. What happens after stopping is covered in our guide to stopping a GLP-1 medication.

Where things are heading

Researchers are working on pill forms and on medicines that act on several hormones at once. We explain the first oral options in this guide, and how these medicines are regulated in this one.

In short

The story of GLP-1 medicines is one of patient lab work: a hormone that disappears in minutes, a lizard peptide that lasts, and engineers who learned to improve on both. It is a reminder that today’s treatments often began as a curious question about something small.

Sources

• Eng J, Kleinman WA, Singh L, Singh G, Raufman JP. Isolation and characterization of exendin-4, an exendin-3 analogue, from Heloderma suspectum venom. Journal of Biological Chemistry, 1992;267(11):7402-7405.
• U.S. Food and Drug Administration. Drug approval records for exenatide (2005), liraglutide (2010, 2014), semaglutide (2017, 2021). Dates were cross-checked across several summaries; confirm against FDA records for formal citation.
• Drucker DJ. The biology of incretin hormones. Cell Metabolism, 2006;3(3):153-165.